The present invention relates to a system of concrete wall forms and the elements used to fabricate the forms.
When pouring concrete to form a concrete wall, forms must be built to hold the wet concrete in proper shape until it has dried and set. A wall form generally comprises two opposing plywood forms or other flat sheet material which define a wall cavity between them. Concrete is poured into the wall cavity and allowed to dry, taking the form of the cavity. The plywood forms must be braced to hold them in place and to prevent them from bowing under the weight of the concrete, and to this end, each plywood form is backed by a support structure. The support structures are tied together by tie rod assemblies spanning the wall cavity between the two plywood forms.
The support structures usually include a series of parallel braces called stringers which are backed by a series of parallel braces called stiffbacks or whalers running at right angles to the stringers. Commonly, lumber such as 2.times.4's or 2.times.8's is used as stringers and whalers. Lumber braces are somewhat bendable and flexible, requiring a large number of stringers and stiffbacks to achieve sufficient support and often requiring additional shoring up. Thus, construction of the forms is tedious and time consuming. Lumber stiffbacks must be nailed to the stringers and they are difficult to shift from side to side if adjustments become necessary.
In some cases builders have used steel or aluminum braces, the most common of which are z-shaped beams or channel beams. Such metal beams cannot be nailed to the wall forms since they have no woodlike nailer surface and must therefore be bolted to the forms and also to the stiffbacks, requiring added time in construction and adjustment. H-shaped extruded beams also have been developed for use as stringers, having attachable nailers for nailing on plywood forms. These beams have the disadvantage that they come in a number of preformed sizes and must be cut down to fit odd lengths of wall.